/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE
 * file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file
 * to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the
 * License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */
package org.apache.tuweni.bytes;

import static com.google.common.base.Preconditions.checkArgument;

final class BytesValues {
    private BytesValues() {}

    static final int MAX_UNSIGNED_SHORT = (1 << 16) - 1;
    static final long MAX_UNSIGNED_INT = (1L << 32) - 1;
    static final long MAX_UNSIGNED_LONG = Long.MAX_VALUE;

    static Bytes fromHexString(CharSequence str, int destSize, boolean lenient) {
        return Bytes.wrap(fromRawHexString(str, destSize, lenient));
    }

    static byte[] fromRawHexString(CharSequence str, int destSize, boolean lenient) {
        int len = str.length();
        CharSequence hex = str;
        if (len >= 2 && str.charAt(0) == '0' && str.charAt(1) == 'x') {
            hex = str.subSequence(2, len);
            len -= 2;
        }

        int idxShift = 0;
        if (len % 2 != 0) {
            if (!lenient) {
                throw new IllegalArgumentException("Invalid odd-length hex binary representation");
            }

            hex = "0" + hex;
            len += 1;
            idxShift = 1;
        }

        int size = len / 2;
        if (destSize < 0) {
            destSize = size;
        } else {
            checkArgument(
                    size <= destSize,
                    "Hex value is too large: expected at most %s bytes but got %s",
                    destSize,
                    size);
        }

        byte[] out = new byte[destSize];

        int destOffset = (destSize - size);
        for (int i = 0; i < len; i += 2) {
            int h = hexToBin(hex.charAt(i));
            int l = hexToBin(hex.charAt(i + 1));
            if (h == -1) {
                throw new IllegalArgumentException(
                        String.format(
                                "Illegal character '%c' found at index %d in hex binary representation",
                                hex.charAt(i), i - idxShift));
            }
            if (l == -1) {
                throw new IllegalArgumentException(
                        String.format(
                                "Illegal character '%c' found at index %d in hex binary representation",
                                hex.charAt(i + 1), i + 1 - idxShift));
            }

            out[destOffset + (i / 2)] = (byte) (h * 16 + l);
        }
        return out;
    }

    private static int hexToBin(char ch) {
        if ('0' <= ch && ch <= '9') {
            return ch - 48;
        } else if ('A' <= ch && ch <= 'F') {
            return ch - 65 + 10;
        } else {
            return 'a' <= ch && ch <= 'f' ? ch - 97 + 10 : -1;
        }
    }
}
